Process for the curing of molding and coating masses based on unsaturated polyesters and copolymerizable monomeric compounds by electron radiation and additionally containing phosphines, arsines and stibines

ABSTRACT

The present invention relates to molding and coating masses comprising mixtures of unsaturated polyesters and copolymerizable monomers which are curable by electron radiation. According to the invention small amounts of phosphines, arsines or stibines are added to such masses, whereby the radiation dose necessary for curing the masses may be remarkably reduced.

United States Patent Wolfgang Metzner Krefeld;

Hans Rudolph, Krefeld-Bockum; Wolfgang Denlnger, Krefeld-Bockum; ManfredPatheiger, Krefeld-uerdingen, all of [72] Inventors [54] PROCESS FOR THECURING OF MOLDING AND COATING MASSES BASED ON UNSATURATED POLYESTERS ANDCOPOLYMERIZABLE MONOMERIC COMPOUNDS BY ELECTRON RADIATION ANDADDITIONALLY CONTAINING PIIOSPIIINES, ARSINES AND STIBINES 2 Claims, NoDrawings [52] U.S. Cl ..204/159.l5, 117/933 l 204/l59.23, 204/l59.24,260/28,

s1 1m.c1...l C08d 1/00, C08f H16 [50] Field ofSearch ..204/l59.l5.159.23, 159.24; 260/865 [56] References Cited UNITED STATES PATENTS3,352,772 ll/I967 Mao 204/159.24 3,331,76I 7/1967 Mao 204/159243,274,291 9/1966 Raichle etal..... 260/865 2,92l,006 H1960 Schmitz etal.204/l59.l5

Primary Examiner-Murray Tillman Assistant Examiner-Richard B. TreverA!t0rneyC0nn0Ily and Hutz ABSTRACT: The present invention relates tomolding and coating masses comprising mixtures of unsaturated polyestersand copolymerizable monomers which are curable by electron radiation.According to the invention small amounts of phosphines, arsines orstibines are added to such masses. whereby the radiation dose necessaryfor curing the masses may be remarkably reduced.

PROCESS FOR THE CURING OF MOLDING AND COATING MASSES BASED ONUNSATURATED POLYESTERS AND COPOLYMERIZABLE MONOMERIC COMPOUNDS BYELECTRON RADIATION AND ADDITIONALLY CONTAINING PHOSPI-IINES, ARSINES ANDSTIBINES Since suitable devices for electron radiation have beenavailable for about 15 years, polymerization of unsaturated compounds,including the curing of polyester molding and coating masses, byelectron radiation has increasingly achieved importance. A detaileddescription of this technique can be found, for example, in the paper Onthe Utilization of Irradiation Processing in Surface Coating and RelatedApplications" published by the firm Radiations Dynamics Inc., WestburyIndustrial Park, Westbury, L.l. NY. 1 l590.

The special advantage of curing by electron radiation mainly consists inthe short time required for curing, compared with conventional methods.A disadvantage of the process consists in that very high radiation dosesare required. High radiation does not only mean a substantial economicburden, they may moreover cause serious destructions of the substratesto be coated. lt is therefore of great interest to reduce the radiationdose required for curing.

Surprisingly, it has been found that the radiation dose can be reducedto about the half by the addition of certain compounds to the moldingand coating masses. Suitable doses amount, for example, from about 5 toabout 50 Mrad.

The object of the invention therefore comprises a process for the curingof molding and coating masses containing unsaturated polyesters andcopolymerisable monomeric compounds, said process comprising irradiatingwith electrons such masses which contain phosphines, arsines or stibinesas initiators.

Examples of such compounds are: triphenyl-phosphine, tritolyl-phosphine,diphenyl-phosphine, dibenzyl-phosphine, dioctyl-phosphine,phenyldimethyl-phosphine, diethylnaphthyl-phosphine, tributyl-phosphine,trioctyl-phosphine, tris-(hydroxyethyl)-phosphine,methylene-bis-diphenyl-phosphine, tricyclopentyl-phosphine,triphenyl-arsine, tribenzylarsine, trioctyl-arsine, triphenyl-stibine,tridiphenyl-stibine, trinaphthyl-stibine and tritolyl-stibine.Triphenyl-phosphine is particularly advantageous.

Molding and coating masses based on unsaturated polyesters andcopolymerisable monomeric compounds with a content of phosphines,arsines and stibines are already described in US. Pat. No. 3,274,291.However, the object of the invention of that specification comprises aprocess for the production of moldings or coatings by curing (at roomtemperature) such masses which have been rendered "nongreening and whichcontain ketone peroxides as catalysts, cobalt salts as accelerators andthe phosphines etc. as coaccelerators. It was not possible to concludetherefrom that phosphines, arsines and stibines would act as initiatorsfor the curing of polyester molding and coating masses by electronradiation.

Unsaturated polyesters in the meaning of the invention comprise, asusual, polycondensation produces obtained from a, B-unsaturateddicarboxylic acids, such as maleic acid, fumaric acid, itaconic acid,mesaconic acid and citraconic acid, with polyhydric alcohols, such asethylene glycol, diethylene glycol, propane, butane-, hexane-diol,trimethylol-propane and pentaerythritol. Part of the unsaturatedcarboxylic acids can be replaced with saturated polybasic carboxylicacids, for example, succinic acid, glutaric acid, adipic acid, phthalicacid, tetrachloro-phthalic acid,hexachloro-endomethylenetetrahydrophthalic acid and trimellitic acid.Other modifications can be achieved by the incorporation of monohydricalcohols, such as butanol and tetrahydrofurfuryl alcohol, and by theincorporation of monobasic acids, such as benzoic acid, oleic linseedoil fatty acid and dehydrated castor oil fatty acid. There may furtherbe mentioned mixtures of unsaturated polyesters with monomericunsaturated compounds containing, besides the radicals of a,B-unsaturated dicarboxylic acids as constituents of the polyesters, alsoa, B-unsaturated ether radicals, be it likewise as constituents of thepolyesters, for example, according to British specification No. 810,222,be it as constituents of other components of the mixture, which are notonly copolymerizable but also air-drying.

Suitable monomeric unsaturated compounds which can be copolymerized withthe unsaturated polyesters are, for example, vinyl compounds, such asstyrene, vinyl-toluene and divinyl-benzene; vinyl esters, such as vinylacetate; unsaturated carboxylic acids and their derivatives, such asacrylic acid, acrylic ester and acrylonitrile; methacrylic acid and itscorresponding derivatives; allyl esters, such as allyl acetate, allylacrylate, phthalic acid diallyl ester, triallyl phosphate and triallylcyanurate.

To increase the stability in storage, the molding masses may containknown inhibitors, for example, p-benzoquinone, 2,5-di-tert-butyl-quinone, hydroquinone, tert-butyl-pyrocatechol,3-methyl-pyrocatechol and 4-ethyl-pyrocatechol, and also coppercompounds, for example, copper naphthenate.

Polymerization catalysts, for example, peroxides, may be added inamounts of about 0.14 percent by weight. Suitable peroxides are, forexample, tert-butyl perbenzoate, dicumyl peroxide, benzoyl peroxide,lauroyl peroxide, methyl ethyl ketone peroxide and cyclohexanoneperoxide. To accelerate the curing, metal compounds such as cobalt,zirconium and vanadium naphthenate, or metal chelates, such as cobaltand zirconium methyl-acetonate, maya be added together with theperoxides. In every case where atmospheric oxygen hinders thepolymerization, paraffin or wax or wax-like substances may be added inknown manner. These substances float during the curing and prevent theaccess of the oxygen inhibiting the polymerization. For working up theseproducts, a combined ultraviolet and electron radiation has provedparticularly valuable.

To protect substrates which are sensitive to light, for example,light-colored woods, small amounts of conventional UV- absorbers may beadded to the molding and coating masses. Furthermore, conventionalcarrier materials and fillers, as well as pigments and thixotropyagents, such as glass fibers, synthetic fibers, silicic acid, talc,titanium dioxide and iron oxide, may be present during the radiationpolymerization. According to the invention, the aforesaid initiators areadded to these polyester molding and coating masses in amounts of 0.1-5percent by weight, preferably 0.5-2.5 percent by weight.

For curing, the said molding and coating masses are irradiated withelectrons. The acceleration voltage must be adapted to the thickness ofthe layer. It can be comprised between about and 3,000 kv. In mostcases, acceleration voltages between 200 and 600 kv. are applied.

The parts given in the following examples are parts by weight.

EXAMPLE l An unsaturated polyester prepared by condensation of 152 partsmaleic acid anhydride, 141 parts phthalic acid anhydride and partspropane-diol-l,2 is mixed with 0.045 parts hydroquinone and dissolved instyrene to give a 65 percent solution. 100 parts of the resultantcoating mass are admixed with 20 parts styrene and 1.5 parts of a 10percent paraffin solution (m.p. 5254 C.). The solution obtained is thendivided: batch A is mixed with 2 percent triphenyl'phosphine, referredto the coating mass; batch B is left without additive.

The two mixtures are then applied to stained Macore wood in layers of500 .t thickness, the coated wood plates are aired and then passed twiceunderneath the scanner of an electron accelerator device (500 kv, 12 m.,distance 5 cm., belt velocity 12 cm./sec.). The radiation dose amountsto about 10 Mrad. lmmediately after irradiation, the coating producedwith batch A is completely cured, whereas that of batch B is still asoft crumbly gel.

EXAMPLE 2 An unsaturated polyester obtained from 1,765 parts maleic acidanhydride, 756 parts glycol, 405 parts 1,3butane-ciiol and 1,540 partstrimethylol-propane diallyl ether in the presence of 0.83 partshydroquinone, is dissolved in styrene to give a 75 percent solution. 100parts of the coating mass so prepared are mixed with 20 parts styreneand 1 part of a cobalt naphthenate solution (Co content 2.2 percent).The resultant isopropyl ether and with the additives according to theinvention set out in the Table. The solutions so obtained are applied ina layer thickness of 500 p. to stained plates of Macore wood. Thecoatings are then pregelled by irradiation with a fluorescent lamp(superactinic, TL-AK 40 W/05 distance 12 cm., duration 90 sec), and thenpassed underneath the scanner of the apparatus described in example I.The results are assembled in the following table:

Sample immediately after an, Percent additive irradiation Smnplu 24 hr.inter N additive Soft, crumbly gel. Soft, crumbly :01.". m| 0.5triphenyl-phosphine Nail-hard Nail in i mu 1.0 triphenyl-phosphine .d0l-ill 2.0 triphenyl-phosphine. .do 135 4.0 triphenyl-phosphine. do. 1702.0 triisopropyl-phosphine. ..do 150 2.0 tricyclohexyl-phosphine,. do150 2.0 tributyl-phosphine d0 .do 122 2.0 triphenyl-arsine Not quitenail-hard, but Not quite nuilhard, but M0 better than without betterthan without EXAMPLE 3 One hundred parts of a coating mass according toexample l are mixed with parts styrene, 1.5 parts of a 10 percentsolution of paraffin (m.p. 5254 C.), 1.5 parts benzoinadditive.

additive.

We claim:

1. A process for curing a molding and coating mass containing (a) anunsaturated polyester comprising the polycondensation product of an a,B-ethylenically unsaturated dicarboxylic acid and a polyhydric alcoholand (b) a copolymerizable unsaturated monomeric compound said processcomprising adding to said mass, a phosphine, an arsine or a stibine asan initiator and irradiating the mass with high energy electrons, theacceleration voltage thereof being from about to about 3,000 kv. and theradiation dose thereof being from about 5 to about 50 Mrad.

2. The process of claim 1 wherein the initiator is present in the massin an amount offrom about 0.1 to about 5 percent by weight.

2. The process of claim 1 wherein the initiator is present in the massin an amount of from about 0.1 to about 5 pErcent by weight.